In the past water-powered gravity type engines have been provided using a reciprocating lever with buckets on each end, the lever being actuated by alternately loading and unloading the buckets as is shown in U.S. Pat. No. 1,260,204. U.S. Pat. No. 4,209,990 discloses a reciprocating lever with a bucket on one end and a counterweight on the other end, together with a ratchet assembly to change the reciprocating motion of the lever to rotary motion. Additionally, power generation systems have been suggested using the closed-loop fluid system wherein a working liquid is alternately vaporized and condensed to drive a turbine. No known prior art has utilized the combination of a reciprocating lever and closed-loop fluid system in a simple yet highly effective thermal-gravity engine as is described in the present invention.